Ken is a liability. Frank is a Labour stooge. Steve is too keen on privatisation. Susan lacks a profile.

The battle lines are being drawn for London's mayoral elections as polling day approaches.

And as the big day gets nearer, the attacks from rival camps will get louder and more vociferous.

Here is BBC News Online's guide to how each of the main candidates will come under attack.

Ken Livingstone, Independent

Campaign slogan: Ken4London

What his supporters say: Ken the brave, the maverick who took on the Labour Party machine but found the electoral process "fixed" against him, and can be trusted to be independent on behalf of Londoners. Only he - now free of the rigours of party membership and with all his experience leading the Greater London Council - truly knows how to put the capital back on the right track.

Ken Livingstone: Can he be trusted?

What his rivals will be saying: A Livingstone victory will see businesses packing up and leaving town in droves.

Mr Livingstone's repeated pledges to never turn his back on Labour and his subsequent decision to effectively do just that prove he can't be trusted.

And does London really want a throwback to the days of the "loony left"?

Mr Livingstone may be determined not to allow those left-wingers outside Labour to attach themselves to his campaign, but attacks on this front are inevitable.

Londoners will also have to be prepared for a history lesson, as press cuttings from Mr Livingstone's days with the GLC are dredged up again, such as his meetings with Sinn Fein (something he points out is now hardly unusual for senior political figures).

Rivals will also say - and are saying - that his bond scheme for the tube would hit Londoners hard in the pocket. They will also insist he is campaigning on his personal profile rather than rock-solid policies for London.

There will also be further comment about his earnings from journalism and the public speaking circuit, not to mention his second home in Brighton, amid Mr Livingstone's own claims that a smear campaign is being conducted against him.

Strong points: Charismatic, popular on the streets of London, backed by endless celebrities and way ahead in the opinion polls.

Weak points: No party machine behind him; some Labour loyalists will never forgive him for standing against the party.

Pie and mash rating: As a Londoner, no one can accuse him of being an outsider. And his success or failure will depend to a large degree on whether a majority of Londoners liked or loathed the GLC.

Counter-attack: His apparently laid back and often sardonic response to all the slings and arrows from rival camps wins him support from cynical Londoners.

Frank Dobson, Labour

Campaign slogan: Frank and to the point

What his supporters say: Frank, straight-talking and serious. No-nonsense solutions to London's many problems.

Frank Dobson: Blair's poodle?

What his rivals will be saying: That he never wanted the job, that he's the Labour Party's second-choice candidate (most grassroots party members wanted Mr Livingstone), that he's prone to the odd gaffe and, perhaps most significantly, that he'd be nothing but Tony Blair's poodle in the mayor's office.

He was, they say, parachuted in to head a campaign he never really wanted to enter, after all.

Mr Dobson has been making an effort to distance himself from Labour headquarters as a result of all this. But, as Mr Livingstone's first campaign poster - suggesting that improving the underground system won't happen by following the party line - showed, it is a line of attack which will be adopted by all his rivals.

Strong points: Ministerial experience and former council leader; backing of the prime minister.

Weak points: Tarnished by Labour's electoral process, widely seen as unfair; backing of the prime minister.

Pie and mash rating: Mr Dobson insists he is a proud Londoner having spent all his adult life there. True, he was born in Yorkshire, but there is a huge chunk of London's population who arrived from elsewhere and wouldn't know their Bow bells from their jellied eels.

Expect, though, candidates with more extensive London backgrounds to subtly make the point.

Counter-attack: Mr Dobson is trying to use Mr Livingstone's apparent lead in the opinion polls to his advantage by suggesting that he is the underdog - and as we all know, everyone loves underdogs.

Steve Norris, Conservative

Campaign slogan: Action not politics

What his supporters say: By concentrating on policies not politics, Steve is the man with the business acumen to bring London roaring back, ending the days of the poorest Londoners living next to the wealthiest inhabitants of the capital.

Steve Norris: Rivals will check out his ministerial record

What his rivals will say: The Norris campaign is playing down his status as official Tory candidate with a series of statements which have sent shivers up the spines of some Conservatives, particularly on section 28 and gay rights.

William Hague plans to hit the campaign trail with Mr Norris, but the candidate has infuriated some Tories.

His tube plans, which include privatisation, will be fertile territory for his rivals, though he brushes them off with disdain.

Mr Norris's "tabloid history" - remember the stories about his many mistresses - will not be far from many minds, but it would take a desperate candidate to refer to it.

However, amid the shambles of the Tories' selection procedure a number of Conservatives didn't want Mr Norris for this very reason.

Opponents will also point out that he was a transport minister in the last Tory government - and will try to blame him for the high cost and long delays to the Jubilee Line Extension.

Pie and mash rating: His business and political background in London more than make up for his Merseyside - rather than London - roots. More London schmoozer than Scouse wideboy.

Counter attack: I'm the only one who really knows how to solve London's transport woes.

Susan Kramer, Liberal Democrat

Campaign slogan: Winning for London

What her supporters say: While those around her bicker in a personality-led contest, Susan, a businesswoman with an impressive CV, is getting down to the nitty-gritty, confronting the issues at the heart of the London elections.

Susan Kramer: Other contenders will tread carefully

What her rivals will say: They will tread carefully, simply because they hope Liberal Democrats thinking of backing Ken Livingstone will change their minds if she puts up a good show - meaning fewer votes for the front-runner.

But if things do turn nasty, expect them to subtly ask "Susan who?" Through no fault of her own, Ms Kramer does not share the high recognition factor of Messrs Livingstone, Dobson and Norris, though the high profile nature of the campaign is changing that.

She will be attacked over her bond scheme for the tube - which she says Mr Livingstone has stolen from her.

Strong points: A business background not tarnished by political wheeler-dealing.

Weak points: A little too earnest for some; battling against high profile rivals.

Pie and mash rating: Born and brought up in London, her decision to stand for mayor followed a particularly frustrating journey on the tube. Many Londoners will sympathise.

Counter-attack: I'm concentrating on the issues while all around me bicker.